Is there a way to make my tiny back teeth bigger?

firstly my front teeth are bigger and I have a bit of a over bite and then all my back teeth are tiny! like kids teeth. I was thinking if I move my lower jaw forward so I don't have a over bite and then if I do that my back teeth wont be touching so maybe feel them in with something so they touch and are bigger? sorry if I am not making sense but I don't know how to explain it better then that :/ is this a silly idea. I don't know what else I can do because it makes my mouth look so small.